A preliminary systematic search for red-clump stars in Galactic open clusters based on 2mass data

Red-clump (RC) giants are intermediate-age, core-helium-burning stars. The RC can be used as a standard candle. In particular, the small variance of the RC's K-band intrinsic luminosity and its weak dependence on chemical composition and age make it an extremely useful distance indicator. In this paper, we use 2mass data to search for RC stars in a sample of 60 Galactic open clusters with known reddening, ages, and distances, and obtain an average value for the RC's absolute K _s-band magnitude, M _{K s} = -1.72 +/- 0.17 mag.